Knight's Circuit Problem in a Chessboard with Holes and its Solution

The solutions to the knight's circuit problem in the 4×n (n≥4) chessboard with two holes are given in this paper. And it is proved that there are knight's circuits in the n×n chessboards with one hole in a corner(when n≥5), or with one hole in the center(when n=3 and n≥7). The solutions or their construction methods are also presented by chaining some chessboards of angle type with different basic chessboards.